Image data communication in image processing system

ABSTRACT

An image processing apparatus comprises: a reception unit adapted to receive image data transmitted from a host computer; first and second communication units adapted to communicate with a second image processing apparatus different from the image processing apparatus; a determination unit adapted to determine a type of image data; and a decision unit adapted to decide, on the basis of determination by the determination unit, whether to use the first communication unit or the second communication unit to transfer the image data.

FIELD OF THE INVENTION

[0001] The present invention relates to an image processing system suchas a network printer and, more particularly, to a system which forms animage on a paper medium in accordance with a PDL print job described ina page description language (PDL).

BACKGROUND OF THE INVENTION

[0002] Conventionally, an image processing system has been used, inwhich an image forming apparatus and image reading apparatus areconnected to an image processing controller connected to a PDLcontroller through a command I/F and Video I/F. The PDL controllercreates raster image data by rasterizing each page of a print jobdescribed in PDL into an image. The command I/F serves to exchangecommands. The Video I/F serves to exchange video image data.

[0003] The PDL controller interprets a PDL job received from a hostcomputer connected through a network or the like to form a raster image,and sends a command sequence generated on the basis of the analysisresult to the image processing controller through the command I/F. ThePDL controller then sends the image data to the image processingcontroller through the Video I/F.

[0004] The image processing controller starts the image formingapparatus to form an image on a paper medium on the basis of thereceived command sequence and image data, and then output the papermedium outside the apparatus (see, for example, Japanese PatentLaid-Open Nos. 8-272555, 10-171617, and 11-240211).

[0005] In this conventional image processing system, image data istransferred by using the Video I/F, which is an image transfer path,regardless of the type of job to be processed. This Video I/F isexclusively designed for the transfer of uncompressed raster image data.When the image forming apparatus is a color printer, the Video I/F isdesigned to transfer 8-bit CMYK (four colors) signals per pixel insynchronism with an image clock. The data transfer rate of the Video I/Fcan be sufficiently increased in accordance with the engine speed. ThisI/F, however, requires dedicated hardware and its control mechanism, andhence leads to an increase in cost.

[0006] In addition, the transfer of image data occupies the Video I/Fregardless of the type of image. Therefore, the next job cannot betransferred unless the transfer of the previous job is completed, evenif the job does not require high image quality or is designed to print ablack-and-white image by using an image forming apparatus capable ofcolor printing. That is, the dedicated hardware is not effectively used.

SUMMARY OF THE INVENTION

[0007] The present invention has been made in consideration of the abovesituation, and has as its object to effectively use a Video I/F which isdedicated hardware and achieve a reduction in cost.

[0008] According to the present invention, the foregoing object isattained by providing an image processing apparatus comprising: areception unit adapted to receive image data transmitted from a hostcomputer; first and second communication units adapted to communicatewith a second image processing apparatus different from the imageprocessing apparatus; a determination unit adapted to determine a typeof image data; and a decision unit adapted to decide, on the basis ofdetermination by the determination unit, whether to use the firstcommunication unit or the second communication unit to transfer theimage data.

[0009] According to the present invention, the foregoing object is alsoattained by providing an image processing apparatus comprising: areception unit adapted to receive image data transmitted from a hostcomputer; a rasterization unit adapted to rasterize the image data;first and second communication units adapted to transmit the image datarasterized by the rasterization unit to a second image processingapparatus different from the image processing apparatus; a determinationunit adapted to determine a type of image data; and a decision unitadapted to decide, on the basis of determination by the determinationunit, whether to use the first communication unit or the secondcommunication unit to transfer the rasterized image data.

[0010] According to the present invention, the foregoing object is alsoattained by providing a data transfer method in an image processingapparatus having first and second communication units adapted tocommunicate with a second image processing method different from theimage processing apparatus comprising: receiving image data transmittedfrom a host computer; determining a type of image data; and deciding, onthe basis of the determined type of image data, whether to use the firstcommunication unit or the second communication unit to transfer theimage data.

[0011] According to the present invention, the foregoing object is alsoattained by providing A data transfer method in an image processingapparatus having first and second communication units adapted tocommunicate with a second image processing method different from theimage processing apparatus comprising: receiving image data transmittedfrom a host computer; rasterizing the image data; determining a type ofimage data; and deciding, on the basis of the determined type of imagedata, whether to use the first communication unit or the secondcommunication unit to transfer the rasterized image data.

[0012] Other features and advantages of the present invention will beapparent from the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

[0014]FIG. 1 is a block diagram showing an arrangement of an imageprocessing system according to embodiments of the present invention;

[0015]FIG. 2 is a flowchart showing a basic flow of operation at thetime of printing in the image processing system according to theembodiments of the present invention;

[0016]FIG. 3 is a flowchart showing an example of the processing ofswitching between compression and noncompression depending on imagequality modes according to a first embodiment of the present invention;

[0017]FIG. 4 is a flowchart showing an example of the processing ofswitching the types of compression depending on color modes according toa second embodiment of the present invention;

[0018]FIG. 5 is a flowchart showing an example of the processing ofbinarizing a black-and-white image according to the second embodiment ofthe present invention;

[0019]FIG. 6 is a block diagram showing another arrangement of the imageprocessing system according to the second embodiment of the presentinvention;

[0020]FIG. 7 is a flowchart showing an example of the processing to beperformed when compression/noncompression switching processing andcompression processing type switching processing are combined accordingto a third embodiment of the present invention; and

[0021]FIG. 8 is a flowchart showing an example of the processing ofswitching communication paths depending on whether or not a securitymode is designated according to a fourth embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Preferred embodiments of the present invention will be describedin detail in accordance with the accompanying drawings.

[0023] (Arrangement of Image Processing System)

[0024]FIG. 1 is a block diagram showing the arrangement of an imageforming system according to the embodiments of the present invention.

[0025] The image forming system according to the embodiments iscomprised of an image processing controller 10, PDL controller 11, imagereading unit 12, and image forming unit 13.

[0026] The image processing controller 10 performs control by using aCPU 101, and includes an HDD 104, a memory (not shown), and the like.The image processing controller 10 also includes a network I/F unit 102for exchanging commands and statuses with the PDL controller 11 and aVideo I/F unit 103 for receiving raster image data from the PDLcontroller 11. The image processing controller 10 is connected to thePDL controller 11 through these I/Fs, and is also connected to the imagereading unit (e.g., a scanner) 12 and image forming unit (e.g., aprinter) 13 through I/Fs (not shown). In addition, the image processingcontroller 10 includes a user I/F unit (not shown) having keys and aliquid crystal display.

[0027] Note that, in the image processing controller 10, dedicated I/Fsare used for the image forming unit 13 and image reading unit 12 and arecomprised of control signals lines and Video data signal lines. A Videodata signal line is a signal line for transmitting or receiving imagedata. A control signal line is a signal line for transmittingtransmission/reception timing control signals for Video data and variouskinds of control instructions to the image reading unit 12 or imageforming unit 13.

[0028] The image reading unit 12 includes a CCD. The image reading unit12 can read an image on an original set on a platen, create digital dataof a raster image, and send it to the image processing controller 10.The image reading unit 12 may include an ADF (automatic document feeder)to continuously read a plurality of originals.

[0029] The image forming unit 13 includes a print engine based on anelectrophotographic scheme, ink-jet scheme, or the like. The imageforming unit 13 can form an image on a paper medium on the basis of theimage data sent from the image processing controller 10, and output themedium outside the apparatus. When the image forming unit 13 includes aplurality of paper feed cassettes, a plurality of different sizes andtypes of media can be selected and fed, and images can be formed on theselected media. The image forming unit 13 may further include a specificfinishing apparatus. In such a case, a plurality of copies of documentscan be sorted and saddle-stitched in the form of a booklet.

[0030] The image processing controller 10 can compress a received image,store the image in the HDD 104, and perform processing such as rotatingit in a desired direction and enlarging or reducing it to a desiredsize. The image processing controller 10 also performs color appearanceadjustment such as smoothing or calibration. The image processingcontroller 10 also includes a memory (not shown) and uses it as a workarea for these processes. The processes are mainly performed in asoftware manner by the programs stored in a ROM (not shown) or the HDD104 operated by the CPU 101. Obviously, however, in order to increasethe processing speed, part of image processing may be implemented byhardware and performed by using the image processing unit in the form ofhardware.

[0031] The PDL controller 11 is controlled by programs operating on aCPU 111. The PDL controller 11 includes an external I/F (not shown) andreceives a print job described in a page description language (PDL) froma host computer through the external I/F. The PDL controller 11 forms aprint job sequence on the basis of the received PDL job, rasterizes animage, and starts the print job. In addition, upon receiving a commandfrom the host computer or the like, the PDL controller 11 can execute ascan job of sending an original read command to the image processingcontroller 10 and sending the received image data to the host computeror the like. A network I/F unit 112 is an I/F for exchanging mainlycommands and statuses with the image processing controller 10. A VideoI/F unit 113 is for transmitting an image to be printed to the imageprocessing controller 10. A memory 114 is used as a work area for theoperation of programs and a frame buffer for temporarily storing theobtained raster image. An HDD (not shown) is also provided to store anOS, programs, job data, and raster images.

[0032] (Operation in Copy Mode)

[0033] The system including the image processing controller 10, imagereading unit 12, and image forming unit 13 shown in FIG. 1 can performcopy operation. When start of copy operation is instructed by the userthrough a user I/F unit (not shown), the image processing controller 10generates a copy job sequence in accordance with a copy mode such as apreset finishing or color mode.

[0034] First of all, the image processing controller 10 outputs an imageread command to the image reading unit 12 to read image data from anoriginal set on the document table (not shown) of the image reading unit12, and temporarily stores the read image data in the HDD 104 or theframe buffer in the memory.

[0035] The image processing controller 10 then outputs a print startcommand to the image forming unit 13, and sends out the image datastored in the HDD 104 or frame buffer in the order based on the copy jobsequence in accordance with the image leading end signal sent from theimage forming unit 13.

[0036] If finishing operation has been designated through the user I/F(not shown), the CPU 101 designates the finishing operation mode at thetime of instructing the print start. The image forming unit 13 startsoperation in accordance with the mode designation, sequentially formssent images on paper media, and outputs them to the finishing apparatus.The finishing apparatus executes finishing operation, such as stapling,bin feeding for each specific number of media, or the like.

[0037] If the image reading unit 12 includes a DF (not shown), imagescan be consecutively read from a plurality of originals set on the DFone by one. The intervals at which originals are read one by one can bedesignated by a program operating on the CPU 101 in accordance with thearrangement of the image processing controller 10. If, for example, theimage processing controller 10 has an HDD 104 or memory with asufficient capacity, all the originals may be read first, and then theimage data of the originals may be sent to the image forming unit 13 oneby one in a desired order in accordance with the form of finishing orthe like. If such a memory does not have a sufficient capacity or thetime taken for the first copy to be output (FCOT) is to be shortened,the image forming unit 13 may be started in synchronism with the startof image read operation to output an image in accordance with the imageleading timing of the image forming unit 13 every time one image isread.

[0038] In addition, in order to solve mismatches between the size anddirection of a read image and those of a paper sheet on which the imageis to be formed, a sequence may be generated such that each image isoutput to the image forming unit 13 after processing such asenlargement/reduction and rotation is performed.

[0039] (I/F between Image Forming Unit and Image Processing Controller)

[0040] The image forming unit 13 in the embodiments can receive colormultilevel image signals and monochromatic (typically, black-and-white)binary image signals as input images. The image forming unit 13 can alsoreceive a 1- or 2-bit TAG signal for each pixel, which represents aproperty of an area in an image.

[0041] In the case of color multilevel images, the image forming unit 13receives a 32-bit signal (8 bits for each of C, M, Y and K signals) perpixel. In this case, a pixel clock is designed to form a 600-dpi imagein accordance with the image forming speed. That is, in the case ofcolor images, images are basically formed at 600 dpi. If, however, a TAGsignal is attached to a specific pixel, an image can be formed withimproved gradation characteristics by decreasing the resolution to 300dpi by pairing two adjacent pixels to one unit. That is, a TAG signal isused as a signal indicating a photographic image area to discriminate itfrom a character area, thereby allowing good image formation inaccordance with the characteristics of the respective areas. As hardwaresignal lines, four (CMYK) 8-bit signal lines and one 1-bit signal line(for TAG), i.e., a total of five signal lines, are provided. Obviously,in addition to them, control signal lines are provided. These signallines may be parallel signal lines. However, a high-speed serial linemay be used to virtually realize 5+α signal lines using drivers at thetwo ends of the line.

[0042] In contrast to this, in the case of black-and-white binaryimages, the image forming unit 13 receives a 1-bit signal per pixel. Inthis case, an image clock is designed to form an image at 1,200 dpi.This image is a black-and-white binary image, and hence has alreadyundergone processing such as dither processing of making an image in aphotographic area have gradation characteristics in the image processingcontroller 10 or PDL controller 11. There is therefore no need to changethe processing in accordance with a TAG bit. No independent line isrequired as a hardware signal line, and the same signal line used totransfer color multilevel images can be commonly used. For example, a1-bit TAG signal line may be used as an image signal line in theblack-and-white binary mode, and may be operated in accordance with adouble-speed clock (quadruple-speed clock considering sub-scanning aswell). Alternatively, the least significant one bit for each of C, M, Yand K signals, i.e., four bits, may be used with the clock equivalent to600 dpi, and image information may be extracted as informationcorresponding to the clock equivalent to 1,200 dpi by using a driver.

[0043] Obviously, in addition to these operations, for example, 8 bits×1color mode may be implemented for a black-and-white multilevel image. Inthis case, of the signal lines for C, M, Y and K signals, only thesignal line for the K signal may be used in addition to the signal linefor a TAG bit.

[0044] (I/F between PDL Controller and Image Processing Controller)

[0045] The first I/Fs between the PDL controller 11 and the imageprocessing controller 10 are the network I/F units 112 and 102 usingEthernet. The two controllers mainly exchange, through these I/Fs,commands such as a print command and mode designation command and statuswhich is information indicating whether or not the image forming unit 13or image reading unit 12 is in an operative state or whether or not anerror or the like has occurred. A general-purpose Ethernet I/F is arelatively low-speed I/F designed to send a relatively small amount ofinformation at a time. However, this I/F uses a general-purpose protocolsuch as TCP/IP, and allows a multi-channel arrangement that exchanges aplurality of types of information at once by setting a plurality ofaddresses and ports. In the system according to the embodiments, eachnetwork I/F has purpose-specific ports such as a print port, managementport, and event port, in parallel, as independent channels. Obviously,this system may have an arrangement using serial lines such as RS232C,USB, or IEEE1394 or parallel lines such as Centronics I/Fs instead ofEthernet.

[0046] The second I/Fs are the Video I/F units 113 and 103 used fortransferring image data. These Video I/F units 113 and 103 are designedto parallelly (logically) send signals such as 8-bit C, M, Y, and Ksignals, a 1-or 2-bit TAG bit signal representing a property of an imagearea, a pixel clock representing a pixel unit of a signal, and a Lineenable signal representing a delimiter for each line. Signal lines maybe provided by a physically necessary number. This, however, results ina thick cable. For this reason, several high-speed serial lines are usedto virtually realize a necessary number of signal lines by using driversat the two ends. Unlike the general-purpose Ethernet I/Fs used as thenetwork I/F units 112 and 102, the Video I/F units 113 and 103 aredesigned exclusively in consideration of the performance of the system,and can transfer data at a sufficiently high rate. However, the VideoI/F units 113 and 103 are of one channel capable of sending one imagedata at a time.

[0047] (Operation in Print Mode in PDL Controller)

[0048]FIG. 2 shows a flow of operation performed in the PDL controller11 when printing is carried out.

[0049] First of all, the PDL controller 11 receives a print job from ahost computer (not shown) through a network I/F or an external I/F (notshown) such as USB or IEEE1394 (step S101). The print job is in the PDLjob form which is described in a so-called page description language(PDL) such as PS, PCL, or LIPS, and is generated from an applicationprogram operating on the host computer or the like through a printdriver. That is, the PDL job includes information (mode designation)required to form a job sequence, for example, the size of paper sheetrequired for each page, a medium, double-sided/single-sided designation,a color mode, and finishing, and image data of each page in the PDLformat.

[0050] The PDL controller 11 extracts the mode designation from thereceived PDL job (step S102), and interprets it to form a job sequencewhich indicates how many paper sheets are to be fed from which paperfeed cassette, which discharge bin paper sheets are to be discharged, ora number of paper sheets after which paper feed cassettes are to beswitched, in accordance with processing such as finishing anddouble-sided printing (step S103).

[0051] In addition, the PDL controller 11 extracts the image dataportion from the PDL job, and converts it into raster image data whichis a bitmap image in the frame buffer area on the memory 114 (stepS104). The obtained raster image data is compressed and temporarilystored in the memory 114 or an HDD (not shown) (step S105). Thisoperation is performed for all the pages of the job.

[0052] The PDL controller 11 notifies the image processing controller 10of the formed job sequence in the form of a command sequence whichimplements the job sequence through the print ports (step S106). Theimage processing controller 10 prepares for image reception by the VideoI/F unit 103 on the basis of the received job sequence. When thepreparation is complete, the image processing controller 10 notifies thePDL controller 11 of the completion of the preparation for the receptionof image data through the print ports.

[0053] Upon confirming the completion of the preparation of thereception of image data in the image processing controller 10 (YES instep S107), the PDL controller 11 transfers image data to the imageprocessing controller 10 through the Video I/F unit 113 in synchronismwith a control signal such as an image clock or Line enable signal (stepS108).

[0054] Transfer processing is performed for each page, and transferstart and end commands are exchanged through the print ports on a pagebasis. If processing by the image processing controller 10 cannot keepup with the transfer rate for some reason, the image processingcontroller 10 notifies the PDL controller 11 of a reception failure, andrequests re-transmission of the image data of the same page. Theprocessing in steps S107 and S108 is continuously repeated until thetransfer of the image data of all the pages is completed (i.e., while NOis obtained in step S109). Upon confirming the completion of thetransfer of the image data of all the pages (YES in step S109), theprint processing by the PDL controller 11 is terminated.

[0055] Note that the process shown in FIG. 2 is merely an example, andwhen image rasterization and storage processing in steps S104 and S105for one page or more are complete, the flow may advance to step S106 toperform command sequence transmission processing so as to transmit thecommand sequence and concurrently perform image data reasterization(step S104) and image data transfer (step S108) during intervals betweencommand transmissions.

[0056] The image data sent from the PDL controller 11 to the imageprocessing controller 10 is temporarily stored in the HDD 104 or thememory (not shown). At this time, the image forming unit 13 is startedafter the reception of all pages or one page or more depending on thesettings of finishing and other various modes in the job sequence.

[0057] In starting the image forming unit 13, the image processingcontroller 10 designates a paper feed cassette and modes such asdouble-sided printing and finishing and arranges page informationassociated with image data in internal queues of the memory (not shown)in the page order required by the operation of the image forming unit 13in accordance with the job sequence transmitted from the PDL controller.At this time, at least image data to be transmitted first is convertedin the frame buffer in the memory, and the remaining image data storedin the HDD 104 are sequentially transferred from the HDD 104 to thememory as soon as the frame buffer becomes empty.

[0058] The image processing controller 10 then sends image data to theimage forming unit 13 in the order of the page information set in thequeues in synchronism with an image leading end signal from the imageforming unit 13. The image forming unit 13 forms images, sent on a pagebasis, on media fed from the designate paper feed cassette, performs thedesignated finishing operation, and delivers the resultant media outsidethe apparatus.

[0059] (Raster Image Data Created by PDL Controller)

[0060] The PDL controller 11 in the embodiments can create two types ofraster image data including a color multilevel image and ablack-and-white binary image. The type of image to be created depends ona designation from a driver on a host computer. If no type isdesignated, the type of image to be created complies with the defaultdesignated in advance in the PDL controller 11.

[0061] If original PDL data to be rasterized is black-and-whitemultilevel data or color multilevel data which is designated to beconverted into black-and-white data by the driver, the rasterizedblack-and-white multilevel image is converted into a black-and-whitebinary image. In this case, the multilevel image is converted into abinary image by using the dither method or the like. In the embodiments,black-and-white binary data is rasterized at 1,200 dpi, and hence theresolution of a character and/or graphic area is changed from 600 dpi to1,200 dpi by smoothing processing, thereby smoothing edges and the like.

[0062] Rasterizing data on the basis of a description by the PDLlanguage makes it possible to discriminate whether a specific area ofthe image is a character/graphic area or a bitmap image such as aphotographic image. In rasterizing a given image, the image processingcontroller 10 also stores such information as area information. Thismakes it possible to use the information for smoothing processing as inthe above case of black-and-white binary images and the generation ofTAG signals for the image processing controller 10.

[0063] (Compression Function)

[0064] The PDL controller 11 includes compression and decompressionfunctions for the obtained raster images. The PDL controller 11compresses black-and-white binary raster image data by a so-called JBIGscheme. The JBIG scheme is a lossless compression scheme, and hence itscompression ratio is not so high. Color multilevel raster image data canbe compressed by the JPEG scheme. The JPEG scheme is a lossy compressionscheme, and hence its compression ratio is high but the image qualitydeteriorates more or less.

[0065] The PDL controller 11 temporarily compresses the raster imagedata and stores it in the HDD (not shown), and rasterizes the image dataagain on the frame buffer in the memory 114 when transferring it via theVideo I/F unit 113. This makes it possible to perform imagerasterization within a processable range in advance even if transfer ofthe previous page is not complete.

[0066] (Image Transfer of Black-and-White Binary Data)

[0067] When the image to be sent from the PDL controller 11 to the imageprocessing controller 10 is a color multilevel image, data correspondingto the number of pixels of (8 bits×4 colors (CMYK)+1 bit (TAG))×1 pageis an image data amount per page. If the image is a black-and-whitebinary image, the image data corresponds to the number of pixelscorresponding to 1 bit×1 page. In addition, in the embodiments, theresolution of a color image is 600 dpi, and the resolution of ablack-and-white image is 1,200 dpi. Therefore, the data amount isreduced to about ⅛.

[0068] Obviously, this data may be transmitted to the image processingcontroller 10 through the Video I/F unit 113. When, however, the dataamount is reduced to such an extent, the data can be compressed andincorporated in a command sequence to the print port upon compression.That is, the image data can be transmitted during the transmission ofthe job sequence through the network I/F unit 112. The image processingcontroller 10 receives the image data concurrently with the jobsequence, and hence need not establish synchronization with the VideoI/F unit 113. This reduces the processing load on the CPU 101.

[0069] (Other Features)

[0070] The PDL controller 11 in the embodiments can process PostScript(PS) as a PDL language. Obviously, the PDL controller 11 can be designedto process a plurality of PDL data such as PCL, PDF, and LIPS data.

[0071] The user can designate the quality of a desired image by thedriver (PPD). In accordance with this designation, the PDL controller 11can adjust the degree of image quality deterioration by adjusting thecompression ratio of the image to be temporarily stored in the HDD.

[0072] In addition, the user can designate color printing orblack-and-white printing through the driver.

[0073] <First Embodiment>

[0074]FIG. 3 is a flowchart showing processing in a PDL controller 11according to the first embodiment of the present invention. Thisprocessing exemplifies a case wherein a high image quality mode and lowimage quality mode are switched in accordance with the image qualitydesignation in a PDL job which is designated through a user I/F such asa print driver. The processing in the flowchart of FIG. 3 will bedescribed in detail below.

[0075] Upon reception of a PDL job from a host computer (not shown), thePDL controller 11 interprets the received PDL job in step S201. The PDLcontroller 11 then generates a command sequence for this PDL job byextracting a mode designation for the job, e.g., the size of each pageand medium designation. This PDL job includes the image quality modedesignation designated by the print driver.

[0076] In step S202, an image quality mode is determined. If this PDLjob corresponds to the high image quality mode designation, the flowadvances to step S203. If the PDL job corresponds to the low imagequality mode, the flow advances to step S207.

[0077] In the high image quality mode, the page description of the PDLjob is interpreted in step S203 to rasterize the data of each page intoraster image data (bitmap image data) on the frame buffer of a memory114.

[0078] The raster image data created in step S204 is then queued in theimage buffer memory (not shown) for transmission in the memory 114. Atthis time, if the buffer memory has a sufficient free space, the imagedata themselves may be queued in the order of pages to be transmitted.In general, however, it is difficult in terms of cost to mount a memoryhaving such a large capacity. Therefore, labels corresponding to theraster image data of the respective pages are queued, and the rasterimage data themselves are compressed and stored in the HDD (not shown)in the PDL controller 11 in association with the labels. Note that eachpage number is uniquely defined in a job, and hence assigning a uniquejob ID to a generated print job can set “job ID+page ID” as a label forraster image data. In this case, a lossless compression algorithm isused, if possible. If only a lossy compression algorithm such as JPEG isallowed to be used in consideration of the HDD capacity, circuitarrangement, and the like, compression is performed by using a highimage quality designation parameter with a compression ratio low enoughto correspond to the high image quality mode. If this image is to betransferred through a Video I/F unit 113, since the image must berasterized, it is important to use a compression scheme that allowshigh-speed rasterization.

[0079] When the rasterization of the image is complete, a commandsequence is transmitted in step S205. Upon reception of the commandsequence, an image processing controller 10 starts preparing for thereception of the image. When the preparation for reception is complete,the image processing controller 10 notifies the PDL controller 11 of thecorresponding information.

[0080] When the notification of the completion of the preparation forreception is received from the image processing controller 10, the flowadvances to step S206 to transfer raster image data as Video data pageby page through the Video I/F unit 113. As described above withreference to the processing in step S204, since the image data queued inthe HDD is compressed, the data must be decompressed before Videotransfer. This decompression processing may be implemented by softwareas long as the processing can be done at a sufficiently high speed inaccordance with the Video transfer rate. In general, hardware dedicatedto decoding is mounted to perform the processing in real time using thehardware. In addition, in this Video transfer, timing commandsindicating a start and end for each page are independently sent throughthe print port.

[0081] Note that since a job is often comprised of a plurality of pages,the rasterization processing and queuing processing in steps S203 andS204 are repeated page by page throughout all the pages, and a commandsequence is then transmitted in step S205. Obviously, another port fortransmitting commands indicating the start and end of image transfer maybe prepared. In this case, after a command sequence is generated in stepS201, the command sequence is quickly transmitted to the imageprocessing controller 10. After the transmission, Video data may be sentto the image processing controller 10 on a page basis while raster imageis created. This allows the image processing controller 10 to know inadvance which type of image is to be sent, and hence can quickly preparefor the reception of the Video data.

[0082] If it is determined in image quality mode determination in stepS202 that the low image quality mode is designated, raster image data iscreated in step S207. In this case, rasterizing image data is the sameprocessing as that performed in step S203.

[0083] The created raster image data is then JPEG-compressed in stepS208. In the first embodiment, in the low image quality mode, sinceimage data is transferred by using a relatively low-speed commandcommunication path, the data is JPEG-compressed in accordance with alossy high compression ratio designation with a higher importance beingplaced on the amount of data than image quality. Using a generalcompression method like JPEG compression allows the image processingcontroller 10 formed as a different hardware to use a generaldecompression method.

[0084] In step S209, the image data of the respective pages which areJPEG-compressed as page data are merged in the command sequencegenerated in step S201. Since a command sequence must be generated on ajob basis instead of a page basis, the processing from the creation ofraster image data in step S207 to merging of compressed image data instep S209 needs to be performed throughout all the pages of the job.

[0085] When a command sequence is generated by merging the image data ofall the pages, the command sequence is transmitted to the imageprocessing controller 10 in step S210. The image processing controller10 can sequentially rasterize images oh a page basis while receiving thecommand sequence without waiting for data from the Video I/F unit 113.

[0086] With the above processing, the data of a multilevel image forwhich high image quality is designated is transmitted through the VideoI/F, whereas a multilevel image for which low image quality isdesignated is JPEG-compressed and transmitted as data attached to acommand through the network I/F. In this manner,compression/noncompression of image data and data transfer paths can beselectively used.

[0087] In general office use or the like in which very high imagequality printing is not required, an image is transferred through acommand communication path unless high image quality is designated.Therefore, the Video I/F, which is low in frequency of use, need not bevery fast, and hence can take a cost-saving arrangement.

[0088] In addition, assume that a port different from a port for thetransmission of a print sequence is provided on a command communicationpath to transmit commands indicating VideoStart/End. In this case, asdescribed above, in the case of a job for which the high image qualitymode is designated, since Video Data transfer is started after a commandsequence is sent, even if the Video I/F is occupied during the Videodata transfer, the next job can be concurrently sent, together withimage data, as long as a low image quality mode sufficient for generaluse is designated for the job.

[0089] The order in which image data are printed by the image processingcontroller 10 can be freely scheduled. If, therefore, an image formingunit 13 is activated in the order in which transfer of image data iscompleted, instead of the order in which command sequences are sent,regardless of the high image quality mode and low image quality mode,the image forming unit 13 can be effectively operated withoutunnecessary pauses.

[0090] As described above, in the case of a job for which high imagequality is not required, image transfer of the job can be done through acommand communication path in a compressed state, and hence can be sentwithout occupying the Video I/F. This makes it possible to effectivelyuse the Video I/F which is dedicated hardware. In addition, decreasingthe operating ratio of the Video I/F allows the use of low-speedhardware, and hence can achieve a reduction in cost.

[0091] <Second Embodiment>

[0092] The second embodiment of the present invention will be describednext. In the second embodiment, compression methods are switched forcolor and black-and-white jobs. This processing will be described withreference to the flowchart of FIG. 4.

[0093] In step S302, a PDL controller 11 interprets the PDL job receivedfrom a host computer (not shown), and generates a command sequence. ThisPDL job includes a color job in which all pages are formed from colorobjects, and a black-and-white job in which all pages are formed fromblack-and-white object data. The PDL job may also include ablack-and-white job designation for printing all pages comprised ofcolor objects in black-and-white.

[0094] In step S303, it is checked whether the received PDL job is acolor or black-and-white job. If the job is a color job, the flowadvances to step S304. If the job is a black-and-white job, the flowadvances to step S306.

[0095] In the case of a color job, the data of each page is rasterizedin step S304. In step S305, the data are JPEG-compressed. Thisprocessing is the same as that described with reference to step S208.

[0096] In the case of a black-and-white job, raster image data iscreated in step S306. This raster image data may be binary data witheach pixel consisting of one bit or multilevel data with each pixelconsisting of eight bits, based on the original description in PDL. Inthe case of a black-and-white job which is based on a color multilevelimage as the original PDL image and in which black-and-white jobdesignation is made, the data is rasterized as multilevelblack-and-white image data with each pixel consisting of eight bits.

[0097] In step S307, binarization processing is performed for theobtained raster image data. The steps in the binarization processing instep S307 will be described in detail with reference to FIG. 5.

[0098] First of all, in step S402, the raster image data obtained instep S306 is interpreted. In step S403, it is checked whether the datais multilevel image data or binary image data.

[0099] In the case of multilevel image data, image area segmentationprocessing is performed in step S404. In the image area segmentationprocessing performed in step S404, TAG bit information indicating eacharea information which has been stored upon PDL data rasterization isused, and a bitmap area is segmented into character areas andphotographic areas in accordance with gradation change patterns.

[0100] In step S405, smoothing processing is performed for a characterarea. In this processing, for example, an 8×8 pixel area is enlargedinto a 16×16 pixel area by pattern matching to smooth edge portions.That is, a 600-dpi raster image is enlarged into a 1,200-dpi image.Obviously, a halftone character which is not in black but is in gray issmoothed without any change in gray level.

[0101] In step S406, an area determined as a photographic area isincreased in the number of pixels. In this processing, one pixel issimply enlarged into four pixels without any change in gray level. Withthe above processing, multilevel data are converted into 1,200-dpi datathroughout the entire image area.

[0102] Thereafter, in step S407, the multilevel image is converted intoa binary image by the dither method or the like. At this time, when aphotographic area is binarized, high-frequency components are removed,and the gradation characteristics slightly deteriorate. Therefore,jaggies caused by conversion from one pixel into four pixels areabsorbed and become less noticeable. That is, better gradationcharacteristics can be obtained by expressing gradation with 1,200-dpibinary data than by 600-dpi binary data.

[0103] If it is determined in step S403 that the obtained image isoriginally a 600-dpi binary image, the flow advances to step S408. Imagearea segmentation processing in step S408 can be done by using only theTAG bit information described above.

[0104] In step S409, smoothing processing is performed for a characterarea as in step S405.

[0105] In step S410, the graininess of a photographic area is reduced byenlarging a 600-dpi binary dither image into 1,200 dpi image. In thisprocessing, the average density of a relatively narrow range of theoriginal image (e.g., a 5×5 pixel area) is calculated, and the density(multilevel value) of the central pixel is set to the average density.The resultant image is slightly blurred. Therefore, filtering may beperformed for edge enhancement, and the number of pixels is thenincreased as in step S406 or S407 to obtain a 1,200-dpi binary image bythe dither method or the like.

[0106] As described above, when the rasterized data is originally binarydata with each pixel consisting of one bit, only smoothing processing isperformed.

[0107] With the above processing, a good 1,200-dpi binaryblack-and-white raster image can be obtained from either black-and-white600-dpi multilevel or binary data.

[0108] When the above binarization processing in step S307 is complete,the binarized image is JBIG-compressed in step S308. The JBIGcompression algorithm is a lossless compression algorithm, and allowsthe original image to be completely reconstructed by decompression.Therefore, no deterioration in image quality is caused by thisalgorithm.

[0109] In step S309, the image data compressed in step S305 or S308 ismerged in a command. In this operation, image data is incorporated inthe command sequence generated in step S302 in addition to a portionwhere information such as a medium and size of each page is described.The command sequence finally generated in this manner internally holdsJPEG- or JBIG-compressed image of each page.

[0110] In step S310, the generated command sequence is transmitted. Theimage processing controller 10 extracts image data from the receivedcommand sequence, JPEG- or JBIG-decompresses the data, and canimmediately perform print processing or storing in the HDD of the data.

[0111] According to the flowchart of FIG. 4, after it is discriminatedwhether a received PDL job is a color or black-and-white job, the datais rasterized. However, color job/black-and-white job determination maybe done after rasterization depending on the structure of a PDLlanguage.

[0112] The second embodiment has exemplified the job in which all thepages are black-and-white or color. However, by performing theprocessing shown in FIG. 4 on a page basis, the present invention can beapplied to a job in which color pages and black-and-white pages areincluded on a page basis.

[0113] In addition, processing for a black-and-white job can be appliedto a monochrome job comprised of monochrome objects as well as ablack-and-white job.

[0114] According to the second embodiment, switching compression methodsfor a color job and black-and-white job enables to transfer image databy using a command communication path in each case. In this case, asshown in FIG. 6, a system can be constructed with an arrangementequivalent to the arrangement shown in FIG. 1 from which the Video I/Funits 103 and 113 are omitted, thereby expecting a great reduction incost.

[0115] In addition, in printing a black-and-white job which is high infrequency of use in offices, in particular, 1,200-dpi binary losslesslycompressed image data is used, and hence a system which can obtain agood print result with respect to a drawing constituted by characters,line drawings, and the like which is especially required in offices, andcan properly cope with color printing which is low in frequency of usecan be built at a low cost.

[0116] As described above, according to the second embodiment,performing image transfer of a black-and-white job by using a commandcommunication path in a compressed state makes it possible to send thejob without occupying the Video I/F. Therefore, the Video I/F which isdedicated hardware can be effectively used. In addition, decreasing theoperation ratio of the Video I/F allows the use of low-speed hardware,and hence can achieve a reduction in cost.

[0117] By performing image transfer of even a color job by using acommand communication path in a compressed state upon increasing thecompression ratio using a lossy compression scheme, the Video I/F can beomitted from the system, thus achieving a reduction in cost.

[0118] <Third Embodiment>

[0119] The third embodiment of the present invention will be describednext.

[0120] In the third embodiment, an example of a combination of the firstand second embodiments will be described with reference to FIG. 7.

[0121] Upon reception of a PDL job from a host computer (not shown), aPDL controller 11 interprets the received PDL job in step S702. Notethat the received PDL job includes a designation indicating a color jobor black-and-white job in addition to an image quality mode.

[0122] In step S703, it is discriminated whether the received PDL job isa color job or black-and-white job. If the job is a color job, the flowadvances to step S704. If the job is a black-and-white job, the flowadvances to step S306.

[0123] In the case of a color job, an image quality mode is determinedin step S704. If a high image quality mode is designated for the PDL job(i.e., a job determined as a color/high image quality mode job), theflow advances to step S203. If the job is a low image quality mode job(i.e., a job determined as a color/low image quality mode job), the flowadvances to step S304.

[0124] In steps S203 to S206, the same processing as that performed insteps S203 to S206 in FIG. 3 is performed. A redundant description ofthis processing is omitted.

[0125] In steps S304 and S305, the same processing as that performed insteps S304 and S305 in FIG. 4 is performed. A redundant description ofthis processing is omitted.

[0126] If it is determined in step S703 that the job is ablack-and-white job, the processing in steps S306 to S308 is performed.The processing in steps S306 to S308 is the same as that shown in FIG.4. In addition, the binarization processing in step S307 is the sameprocessing as that described with reference to FIG. 5 in the secondembodiment, and hence a redundant description thereof is omitted.

[0127] In step S309, the image data compressed in step S305 or S308 ismerged in a command. In step S310, the generated command sequence istransmitted. These processes are also the same as those described in thesecond embodiment.

[0128] In the third embodiment, a black-and-white job uses an engine foroutputting 1,200-dpi binary image data. For this reason, only color jobsare selectively processed in the high image quality and low imagequality mode. However, black-and-white jobs may also be selectivelyprocessed in the high image quality mode and low image quality modedepending on the embodiment of an engine.

[0129] According to the third embodiment, since the Video I/F is notused even for a color job as long as it is in the low image qualitymode, the frequency of use of the Video I/F further decreases. Thismakes it possible to use a more inexpensive low-speed arrangement and tooutput images with a high image quality of 1,200 dpi in the case ofblack-and-white jobs.

[0130] As described above, according to the third embodiment, in thecase of a job for which high image quality is not required or ablack-and-white job, image transfer of the job can be done through acommand communication path in a compressed state, and hence can be sentwithout occupying the Video I/F. This makes it possible to effectivelyuse the Video I/F which is dedicated hardware. In addition, decreasingthe operating ratio of the Video I/F allows the use of low-speedhardware, and hence can achieve a reduction in cost.

[0131] Obviously, this system can be designed to allow the user todesignate an image quality mode or color mode through the print driverat the time of printing. Alternatively, the user may be allowed to setin advance usable modes through the PDL controller.

[0132] It is needless to say that monochrome data can be used in placeof black-and-white data.

[0133] In addition, it is obvious that the image forming unit can bedesigned to process jobs without discriminating color jobs fromblack-and-white jobs. In such case, when an original mainly containing aphotograph is to be processed, the high image quality mode using theVideo I/F may be set. When an original mainly containing texts is to beprocessed, even if it is a color original, the original data may bebinarized and losslessly compressed. Image transfer of the resultantdata may be performed through a command communication path to print thedata at 1,200 dpi.

[0134] <Fourth Embodiment>

[0135] The fourth embodiment of the present invention will be describednext.

[0136] In the fourth embodiment, the PDL job transmitted from a hostcomputer is processed by switching between data transfer through a VideoI/F and data transfer through a network I/F depending on whether or nota security mode is designated.

[0137]FIG. 8 is a flowchart showing the flow of processing in the fourthembodiment.

[0138] The basic flow is the same as the flowchart of FIG. 3 in thefirst embodiment. Referring to FIG. 3, in step S202, an image qualitymode is determined to determine the high image quality mode or low imagequality mode. In contrast to this, in the fourth embodiment, it ischecked in step S802 whether or not the security mode is designated.

[0139] In step S801, the PDL job received from the host computer isinterpreted. If it is determined in step S802 that the security mode isdesignated, the flow advances to step S203 to transfer data through theVideo I/F. If it is determined in step S802 that the security mode isnot designated, the flow advances to step S207 to transfer data throughthe network I/F.

[0140] In steps S203 to S210, the same processing as that performed inS203 to S210 in FIG. 3 is performed. Therefore, a redundant descriptionof this processing is omitted.

[0141] The fourth embodiment has been described above. This embodimentallows selective use of communication paths depending on whether or notthe PDL job transmitted from the host computer designates the securitymode.

[0142] The flowchart of FIG. 8, with reference to which the fourthembodiment is described, has exemplified the case wherein the Video I/Fis used when the security mode is designated. However, when the securitymode is designated, data may be transferred through the network I/F,whereas when the security mode is not designated, data may betransferred through the Video I/F.

[0143] In either case, if the security of a communication path used totransfer a job for which the security mode is designated is improved,the job for which the security mode is designated can be selectivelytransferred in safety.

[0144] <Other Embodiments>

[0145] Note that the present invention can be applied to an apparatuscomprising a single device or to system constituted by a plurality ofdevices.

[0146] Furthermore, the invention can be implemented by supplying asoftware program, which implements the functions of the foregoingembodiments, directly or indirectly to a system or apparatus, readingthe supplied program code with a computer of the system or apparatus,and then executing the program code. In this case, so long as the systemor apparatus has the functions of the program, the mode ofimplementation need not rely upon a program.

[0147] Accordingly, since the functions of the present invention areimplemented by computer, the program code installed in the computer alsoimplements the present invention. In other words, the claims of thepresent invention also cover a computer program for the purpose ofimplementing the functions of the present invention.

[0148] In this case, so long as the system or apparatus has thefunctions of the program, the program may be executed in any form, suchas an object code, a program executed by an interpreter, or scrip datasupplied to an operating system.

[0149] Example of storage media that can be used for supplying theprogram are a floppy disk, a hard disk, an optical disk, amagneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a magnetic tape, anon-volatile type memory card, a ROM, and a DVD (DVD-ROM and a DVD-R).

[0150] As for the method of supplying the program, a client computer canbe connected to a website on the Internet using a browser of the clientcomputer, and the computer program of the present invention or anautomatically-installable compressed file of the program can bedownloaded to a recording medium such as a hard disk. Further, theprogram of the present invention can be supplied by dividing the programcode constituting the program into a plurality of files and downloadingthe files from different websites. In other words, a WWW (World WideWeb) server that downloads, to multiple users, the program files thatimplement the functions of the present invention by computer is alsocovered by the claims of the present invention.

[0151] It is also possible to encrypt and store the program of thepresent invention on a storage medium such as a CD-ROM, distribute thestorage medium to users, allow users who meet certain requirements todownload decryption key information from a website via the Internet, andallow these users to decrypt the encrypted program by using the keyinformation, whereby the program is installed in the user computer.

[0152] Besides the cases where the aforementioned functions according tothe embodiments are implemented by executing the read program bycomputer, an operating system or the like running on the computer mayperform all or a part of the actual processing so that the functions ofthe foregoing embodiments can be implemented by this processing.

[0153] Furthermore, after the program read from the storage medium iswritten to a function expansion board inserted into the computer or to amemory provided in a function expansion unit connected to the computer,a CPU or the like mounted on the function expansion board or functionexpansion unit performs all or a part of the actual processing so thatthe functions of the foregoing embodiments can be implemented by thisprocessing.

[0154] As many apparently widely different embodiments of the presentinvention can be made without departing from the spirit and scopethereof, it is to be understood that the invention is not limited to thespecific embodiments thereof except as defined in the appended claims.

What is claimed is:
 1. An image processing apparatus comprising: areception unit adapted to receive image data transmitted from a hostcomputer; first and second communication units adapted to communicatewith a second image processing apparatus different from the imageprocessing apparatus; a determination unit adapted to determine a typeof image data; and a decision unit adapted to decide, on the basis ofdetermination by said determination unit, whether to use said firstcommunication unit or said second communication unit to transfer theimage data.
 2. The apparatus according to claim 1, wherein saiddetermination unit determines an image quality mode of the image data,and said decision unit decides to use said first communication unit totransfer the image data when said determination unit determines a highimage quality mode, and to use said second communication unit totransfer the image data when said determination unit determines a lowimage quality mode.
 3. The apparatus according to claim 2, wherein whensaid determination unit determines the low image quality mode, the imagedata is compressed and transferred by using said second communicationunit.
 4. The apparatus according to claim 1, wherein said determinationunit determines whether or not a security mode is designated in theimage data, and said decision unit decides to use said firstcommunication unit to transfer the image data when said determinationunit determines that the security mode is designated, and to use saidsecond communication unit to transfer the image data when saiddetermination unit determines that the security mode is not designated.5. The apparatus according to claim 1, wherein said first communicationunit comprises an interface for image data transfer, and said secondcommunication unit comprises a general-purpose network interface.
 6. Animage processing apparatus comprising: a reception unit adapted toreceive image data transmitted from a host computer; a rasterizationunit adapted to rasterize the image data; first and second communicationunits adapted to transmit the image data rasterized by saidrasterization unit to a second image processing apparatus different fromthe image processing apparatus; a determination unit adapted todetermine a type of image data; and a decision unit adapted to decide,on the basis of determination by said determination unit, whether to usesaid first communication unit or said second communication unit totransfer the rasterized image data.
 7. The apparatus according to claim6, wherein said first communication unit comprises communication unitfor communicating data rasterized by said rasterization unit, and saidsecond communication unit comprises a communication unit forcommunicating a command based on the image data.
 8. The apparatusaccording to claim 7, wherein said determination unit determines animage quality mode of the image data, and said decision unit decides touse said first communication unit to transfer the image data when saiddetermination unit determines a high image quality mode, and to use saidsecond communication unit to transfer the image data when saiddetermination unit determines a low image quality mode.
 9. The apparatusaccording to claim 6, wherein said determination unit determines whetheror not a security mode is designated in the image data, and saiddecision unit decides to use said first communication unit to transferthe image data when said determination unit determines that the securitymode is designated, and to use said second communication unit totransfer the image data when said determination unit determines that thesecurity mode is not designated.
 10. A data transfer method in an imageprocessing apparatus having first and second communication units adaptedto communicate with a second image processing method different from theimage processing apparatus comprising: receiving image data transmittedfrom a host computer; determining a type of image data; and deciding, onthe basis of the determined type of image data, whether to use saidfirst communication unit or said second communication unit to transferthe image data.
 11. The method according to claim 10, wherein an imagequality mode of the image data is determined in said determining thetype of image data, and it is decided to use said first communicationunit to transfer the image data when a high image quality mode isdetermined as the type of image data, and to use said secondcommunication unit to transfer the image data when a low image qualitymode is determined as the type of image data.
 12. The method accordingto claim 11, wherein when the low image quality mode is determined asthe type of image data, the image data is compressed and transferred byusing said second communication unit.
 13. The method according to claim10 further comprising determining whether or not a security mode isdesignated in the image data, wherein it is decided to use said firstcommunication unit to transfer the image data when the security mode isdesignated, and to use said second communication unit to transfer theimage data when the security mode is not designated.
 14. The methodaccording to claim 10, wherein said first communication unit comprisesan interface for image data transfer, ands said second communicationunit comprises a general-purpose network interface.
 15. A data transfermethod in an image processing apparatus having first and secondcommunication units adapted to communicate with a second imageprocessing method different from the image processing apparatuscomprising: receiving image data transmitted from a host computer;rasterizing the image data; determining a type of image data; anddeciding, on the basis of the determined type of image data, whether touse said first communication unit or said second communication unit totransfer the rasterized image data.
 16. The method according to claim15, wherein said first communication unit comprises a communication unitfor communicating rasterized data, and said second communication unitcomprises a communication unit for communicating a command based on theimage data.
 17. The method according to claim 16, wherein an imagequality mode of the image data is determined in said determining thetype of image data, and it is decided to use said first communicationunit to transfer the image data when said determination unit determinesa high image quality mode, and to use said second communication unit totransfer the image data when said determination unit determines a lowimage quality mode.
 18. The method according to claim 15 furthercomprising determining whether or not a security mode is designated inthe image data, wherein it is decided to use said first communicationunit to transfer the image data when the security mode is designated,and to use said second communication unit to transfer the image datawhen the security mode is not designated.
 19. A storage medium readableby a data processing apparatus, said storage storing a program which isexecutable by the data processing apparatus and comprises program codesrealizing the data transfer method described in claim
 10. 20. A storagemedium readable by a data processing apparatus, said storage storing aprogram which is executable by the data processing apparatus andcomprises program codes realizing the data transfer method described inclaim 15.